Matthew, I hope you still read this thread and I hope your marriage is going well.
I'm in exactly the same boat. My wife is an evangelical. I'm an agnostic, because I think being hard-lined atheist is almost as close minded as being Christian, because we just don't know everything. But I subscribe to mostly atheistic beliefs. And my wife is a hard-lined evangelical Christian. My dad is a pastor, my uncle is a pastor, my brother will be ordained in a couple months and will be an Army chaplain in August.
Around my family, my wife and church people, I tell them I'm Christian. Funnily enough, I even teach Sunday School.
For me, I rationalize it this way. I love my family. I love my wife. My wife's social circle is the church. I think keeping a happy home and a happy family is more important than the few hours a week I need to go to church or the animosity caused by my fervently extolling my beliefs.
Many people sit on their own soap boxes and say they would never "sell out" their beliefs. But when I prioritize my life, it goes 1) Wife & kids 2) family 3) security 4) friends 5) beliefs. I'm willing to sacrifice convincing those in my family or church for overall happiness of their and my life. And once my kids get old enough, they will be getting an alternate education from me, but also, I will teach them about maintaining a happy family.
My wife knows that I was agnostic and she knows I still hold tenets like evolution, big bang, etc., but I tell her that I think it's just Genesis taken figuratively. It saves a lot of arguing between us. I tell her and my family I'm born again, I just think that the Bible shouldn't be taken 100% literally. And that opens up thoughtful discussion without the animosity.
So, do what's right for you and your situation.